Method, mobile communications device, system and circuitry for estimating an occupancy level of a shared channel

ABSTRACT

A method determining indication of an occupancy level in a mobile communications system including a base station to communicate with a mobile communications device via a wireless interface provided by a first frequency channel allocated to mobile networks communications for the mobile communications system and by a shared channel which can be shared by the mobile communications system and by other wireless communications systems. The method includes: a mobile communications device: measuring, for each of plural first time periods within a second time period, a channel utilization on the shared channel; determining channel occupancy states for the shared channel for each of the first time periods based on the measured channel utilization; and determining an indication of an occupancy level for the shared channel for the second time period, the indication of an occupancy level determined based on the occupancy states for the shared channel for each first time period.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/458,765, filed Jul. 1, 2019, which is a continuation of U.S.application Ser. No. 15/323,586, filed Jan. 3, 2017 (now U.S. Pat. No.10,375,592), which is based on PCT filing PCT/EP2015/066962, filed Jul.24, 2015, and claims priority to EP 14178654.1, filed Jul. 25, 2014, theentire contents of each are incorporated herein by reference.

BACKGROUND Field

The present disclosure relates to a method of determining an indicationof an occupancy level in a mobile communications system, a mobilecommunications device for use in a mobile communications system, amobile communications system and circuitry for a mobile communicationsdevice for use in a mobile telecommunications system.

Description of Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

It is well known in the field of wireless telecommunications for regionsof the radio spectrum to be assigned to different mobile networkoperators (MNO) for their exclusive use through a license. A licensetypically grants an MNO exclusive use over a number of years of apredefined portion of the radio frequency spectrum in which to deploy amobile communications network (e.g. GSM, WCDMA/HSPA, LTE/LTE-A). Forexample, LTE frequencies are conventionally allocated exclusively tomobile networks communications (e.g. LTE communications) and, in turn,the LTE frequencies may be divided into bands which can themselves beallocated exclusively to one or more mobile operators. As a result ofthis approach, an operator has guarantees of no other radio servicesinterfering with the radio resources that have been assigned to theoperator, and within the limitations of the license conditions it hasexclusive control over what radio technology it deploys in the network.Consequently, a wireless telecommunications system that is primarilydesigned to operate using radio resources that have been licensed forexclusive use by the wireless telecommunications system can operate witha degree of centralised control and coordination to help make mostefficient use of the available radio resources. Such a wirelesstelecommunication system also manages all the interference internally,based on standard specifications, since the licence grants it goodimmunity from external interference sources. Coexistence of differentdevices deployed on an MNO's licensed band is managed throughconformance to relevant radio standards. Licensed spectrum is todayusually assigned to operators via government-organised auctions, butso-called “beauty contests” continue also to be in use.

It is also well known in the field of wireless telecommunications forregions of the available radio spectrum to remain unlicensed. Unlicensed(licence exempt) radio spectrum may, at least to some extent, be freelyused by a number of different technologies, such as Wi-Fi and Bluetoothand other non-3GPP radio access technologies. Operating parameters fordevices using unlicensed spectrum bands are typically stipulated bytechnical regulatory requirements such as e.g. the FCC Part 15 rule for2.4 GHz ISM band. Coexistence of different devices deployed onunlicensed band, due to the lack of centralised coordination andcontrol, is usually based on such technical rules and various politenessprotocols.

The use of wireless telecommunications system technologies designed foroperation on licensed radio spectrum, such as LTE, is becoming more andmore prevalent, both in terms of increasing take-up of established usesfor wireless telecommunications technologies, and also the introductionof new uses, e.g., in the developing field of machine-typecommunications (MTC). In order to help provide more bandwidth to supportthis increased use of wireless telecommunications technologies, it hasrecently been proposed to use unlicensed radio spectrum resources tosupport operations on licensed radio spectrum.

However, in contrast to licensed spectrum, unlicensed spectrum can beshared and used among different technologies, or different networksusing the same technology, without any co-ordinated/centralised control,for example to provide protection against interference. As a consequenceof this, the use of wireless technologies in unlicensed spectrum can besubject to unpredictable interference and has no guarantees of spectrumresources, i.e. the radio connection takes place on a best effort basis.This means that wireless network technologies, such as LTE, which aregenerally designed to operate using licensed radio resources, requiremodified approaches to allow them to efficiently use unlicensed radioresources, and in particular to co-exist reliably and fairly with otherradio access technologies that may be simultaneously operating in theunlicensed spectrum band.

Likewise, in a system where a spectrum has been licensed to more thanone party, e.g. two MNOs, each MNO does not have exclusive use of thespectrum and the spectrum is shared between them. The communicationsfrom one MNO can interfere with the communications from the other MNOand while each MNO can try to reduce the interference level within theirown network, they have no direct control over the communications fromthe other MNO's communications.

Therefore, deploying a mobile radio access technology system primarilydesigned to operate in licensed spectrum bands (i.e. having exclusiveaccess to, and hence a level of control over, the relevant radioresources) in a manner which is required by operation in a shared(unlicensed or licensed) spectrum bands (i.e. without having exclusiveaccess to at least some of the relevant radio resources), gives rise tonew technical challenges.

SUMMARY

According to an aspect of the disclosure there is provided a method ofdetermining an indication of an occupancy level in a mobilecommunications system, wherein the mobile communications systemcomprises a base station arranged to communicate with a mobilecommunications device via a wireless interface provided by a firstfrequency channel allocated to mobile networks communications for themobile communications system and by a shared channel which can be sharedby the mobile communications system and by other wireless communicationssystems. The method comprising a mobile communications device:measuring, for each of a plurality of first time periods within a secondtime period, a channel utilisation on the shared channel; determiningchannel occupancy states for the shared channel for each of the firsttime periods based on the measured channel utilisation; and determiningan indication of an occupancy level for the shared channel for thesecond time period, wherein the indication of an occupancy level isdetermined based on the occupancy states for the shared channel for eachof the first time periods.

The mobile communications device may generate a measurement report basedon the indication of an occupancy level for the shared channel andtransmit the measurement report to the base station. For example, themobile communications device may detect that the shared channel iscongested when an occupancy level for the shared channel is estimated tobe above a congestion threshold; and may, upon detecting that the sharedchannel is congested, generate and transmit the measurement report. Uponreceipt of the measurement report, the mobile communications system maydetermine whether to activate or deactivate the shared channel foruplink and/or downlink communications with mobile communications devicesbased on the indication of an occupancy level for the shared channel. Ameasurement report may be transmitted at one or more of the followingtimes: periodically, upon receipt of a measurement request, at arandomly selected time or when one or more predetermined events occur.

The indication of an occupancy level may be determined at one or more ofthe following times: periodically, upon receipt of a measurementrequest, at a randomly selected time or when one or more predeterminedevents occur.

In the above paragraphs, “a predetermined event” may comprise one of: amobile communications device being powered up, a mobile communicationdevice experiencing congestion on a frequency channel, a mobilecommunication device experiencing congestion in a time period, a mobilecommunication device experiencing congestion on a channelization code, auser request, a mobile communications network request, the expiry of atimer and a mobile communication device having a low utilisation level.

The mobile communications device measuring a channel utilisation on theshared channel may comprise determining whether the mobilecommunications system is transmitting signals on the shared channel,when it is determined that the mobile communications system istransmitting signals on the shared channel, measuring the channelutilisation based on an interference measurement indicating aninterference level identified for the signals transmitted on the sharedchannel by the mobile communications system; and when it is determinedthat the mobile communications system is not transmitting signals on theshared channel, measuring the channel utilisation based on a measurementindicating a power received via the shared channel.

The mobile communications device may comprise a first transceiveroperable to receive shared channel signals with the base station using afirst technology and a second transceiver operable to receive sharedchannel signals using a second technology, the second technology beingdifferent from the first technology. The method may then comprise themobile communications device measuring the channel utilisation based ona first channel utilisation derived from signals received by the firsttransceiver and on a second channel utilisation derived from signalsreceived by the second transceiver.

According to another aspect of the present disclosure, there may beprovided a mobile communications device for use in a mobilecommunications system, the system comprising a base station arranged tocommunicate with mobile communications devices via a wireless interfaceprovided by a first frequency channel allocated to mobile networkscommunications for the mobile communications system and by a sharedfrequency channel which can be used by the mobile communications systemand by other wireless communications systems. The mobile communicationsdevice comprises a controller unit and a transceiver unit fortransmitting and receiving signals via the wireless interface. Thecontroller unit is configured to: measure, for each of a plurality offirst time periods within a second time period, a channel utilisation onthe shared channel based on signals received by the transceiver unit;determine channel occupancy states for the shared channel for each ofthe first time periods based on the measured channel utilisation; anddetermine an indication of an occupancy level for the shared channel forthe second time period, wherein the indication of an occupancy level isdetermined based on the occupancy states for the shared channel for eachof the first time periods.

According to a further aspect of the present disclosure, there isprovided a mobile communications system comprising a base stationarranged to communicate with mobile communications devices via awireless interface provided by a first frequency channel allocated tomobile networks communications for the mobile communications system andby a shared frequency channel which can be used by the mobilecommunications system and by other wireless communications systems; anda first mobile communications device. The mobile communications deviceis configured to measure, for each of a plurality of first time periodswithin a second time period, a channel utilisation on the sharedchannel; determine channel occupancy states for each of the first timeperiods and for the shared channel based on the measured channelutilisation; and determine an indication of an occupancy level for thesecond time period and for the shared channel wherein the indication ofan occupancy level is determined based on the occupancy states for theshared channel for each of the first time periods.

According to yet another aspect of the present disclosure, there isprovided circuitry for a mobile communications device for use in amobile telecommunications system, the system comprising a base stationarranged to communicate with mobile communications devices via awireless interface provided by a first frequency channel allocated tomobile network communications for the mobile communications system andby a shared frequency channel which can be used by the mobilecommunications system and by other wireless communications systems. Thecircuitry comprises a controller element and a transceiver elementconfigured to operate together to: measure, for each of a plurality offirst time periods within a second time period, a channel utilisation onthe shared channel based on signals received by the transceiver unit;determine channel occupancy states for the shared channel for each ofthe first time periods based on the measured channel utilisation; anddetermine an indication of an occupancy level for the shared channel forthe second time period, wherein the indication of an occupancy level isdetermined based on the occupancy states for the shared channel for eachof the first time periods.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described examples, together with further advantages, willbe best understood by reference to the following detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein likereference numerals designate identical or corresponding parts throughoutthe several views, and wherein:

FIG. 1 provides a schematic diagram illustrating an example of a mobiletelecommunication system;

FIG. 2 provides a schematic diagram illustrating a LTE radio frame;

FIG. 3 provides a schematic diagram illustrating an example of a LTEdownlink radio subframe;

FIG. 4 schematically represents a wireless telecommunications system;

FIG. 5 provides a schematic illustration of a channel occupancymeasurement;

FIG. 6 provides a schematic flowchart of a method of measuring and ofreporting occupancy;

FIG. 7 provides a schematic time diagram showing an example use of aquiet time;

FIG. 8 provides a schematic time diagram showing another example use ofquiet times;

FIG. 9 provides a schematic illustration of another channel occupancymeasurement; and

FIG. 10 provides a signalling ladder diagram representing communicationsbetween a base station and a terminal device.

DETAILED DESCRIPTION OF EXAMPLES

FIG. 1 provides a schematic diagram illustrating some basicfunctionality of a mobile telecommunications network/system 100operating in accordance with LTE principles and which may be adapted toimplement examples of the disclosure as described further below. Variouselements of FIG. 1 and their respective modes of operation arewell-known and defined in the relevant standards administered by the3GPP (RTM) body, and also described in many books on the subject, forexample, Holma H. and Toskala A [1]. It will be appreciated thatoperational aspects of the telecommunications network which are notspecifically described below may be implemented in accordance with anyknown techniques, for example according to the relevant standards.

The network 100 includes a plurality of base stations 101 connected to acore network 102. Each base station provides a coverage area 103 (i.e. acell) within which data can be communicated to and from terminal devices104. Data is transmitted from base stations 101 to terminal devices 104within their respective coverage areas 103 via a radio downlink. Data istransmitted from terminal devices 104 to the base stations 101 via aradio uplink. The uplink and downlink communications are made usingradio resources that are licenced for use by the operator of the network100. The core network 102 routes data to and from the terminal devices104 via the respective base stations 101 and provides functions such asauthentication, mobility management, charging and so on. Terminaldevices may also be referred to as mobile stations, user equipment (UE),user terminal, mobile radio, and so forth. Base stations may also bereferred to as transceiver stations/nodeBs/e-nodeBs, and so forth.

Mobile telecommunications systems such as those arranged in accordancewith the 3GPP defined Long Term Evolution (LTE) architecture use anorthogonal frequency division modulation (OFDM) based interface for theradio downlink (so-called OFDMA) and a single carrier frequency divisionmultiple access scheme (SC-FDMA) on the radio uplink. FIG. 2 shows aschematic diagram illustrating an OFDM based LTE downlink radio frame201. The LTE downlink radio frame is transmitted from a LTE base station(known as an enhanced Node B) and lasts 10 ms. The downlink radio framecomprises ten subframes, each subframe lasting 1 ms. A primarysynchronisation signal (PSS) and a secondary synchronisation signal(SSS) are transmitted in the first and sixth subframes of the LTE frame.A physical broadcast channel (PBCH) is transmitted in the first subframeof the LTE frame.

FIG. 3 is a schematic diagram of a grid which illustrates the structureof an example conventional downlink LTE subframe. The subframe comprisesa predetermined number of symbols which are transmitted over a 1 msperiod. Each symbol comprises a predetermined number of orthogonalsubcarriers distributed across the bandwidth of the downlink radiocarrier.

The example subframe shown in FIG. 3 comprises 14 symbols and 1200subcarriers spread across a 20 MHz bandwidth licenced for use by theoperator of the network 100, and this example is the first subframe in aframe (hence it contains PBCH). The smallest allocation of physicalresource for transmission in LTE is a resource block comprising twelvesubcarriers transmitted over one subframe. For clarity, in FIG. 3, eachindividual resource element is not shown, instead each individual box inthe subframe grid corresponds to twelve subcarriers transmitted on onesymbol.

FIG. 3 shows in hatching resource allocations for four LTE terminals340, 341, 342, 343. For example, the resource allocation 340 for LTEterminal UE 4 extends over five blocks of twelve subcarriers (i.e. 60subcarriers), the resource allocation 343 for LTE terminal UE2 extendsover six blocks of twelve subcarriers (i.e. 72 subcarriers), and so on.

Control channel data can be transmitted in a control region 300(indicated by dotted-shading in FIG. 3) of the subframe comprising thefirst “n” symbols of the subframe where “n” can vary between one andthree symbols for channel bandwidths of 3 MHz or greater and where “n”can vary between two and four symbols for a channel bandwidth of 1.4MHz. For the sake of providing a concrete example, the followingdescription relates to host carriers with a channel bandwidth of 3 MHzor greater so the maximum value of “n” will be 3 (as in the example ofFIG. 3). The data transmitted in the control region 300 includes datatransmitted on the physical downlink control channel (PDCCH), thephysical control format indicator channel (PCFICH) and the physical HARQindicator channel (PHICH). These channels transmit physical layercontrol information. Control channel data can also or alternatively betransmitted in a second region of the subframe comprising a number ofsubcarriers for a time substantially equivalent to the duration of thesubframe, or substantially equivalent to the duration of the subframeremaining after the “n” symbols. The data transmitted in this secondregion is transmitted on the enhanced physical downlink control channel(EPDCCH). This channel transmits physical layer control informationwhich may be in addition to that transmitted on other physical layercontrol channels.

PDCCH and EPDCCH contain control data indicating which subcarriers ofthe subframe have been allocated to specific terminals (or all terminalsor subset of terminals). This may be referred to as physical-layercontrol signalling/data. Thus, the PDCCH and/or EPDCCH data transmittedin the control region 300 of the subframe shown in FIG. 3 would indicatethat UE1 has been allocated the block of resources identified byreference numeral 342, that UE2 has been allocated the block ofresources identified by reference numeral 343, and so on.

PCFICH contains control data indicating the size of the control region(i.e. between one and three symbols for channel bandwidths of 3 MHz orgreater and between two and four symbols for channel bandwidths of 1.4MHz).

PHICH contains HARQ (Hybrid Automatic Request) data indicating whetheror not previously transmitted uplink data has been successfully receivedby the network.

Symbols in a central band 310 of the time-frequency resource grid areused for the transmission of information including the primarysynchronisation signal (PSS), the secondary synchronisation signal (SSS)and the physical broadcast channel (PBCH). This central band 310 istypically 72 subcarriers wide (corresponding to a transmission bandwidthof 1.08 MHz). The PSS and SSS are synchronisation signals that oncedetected allow a LTE terminal device to achieve frame synchronisationand determine the physical layer cell identity of the enhanced Node Btransmitting the downlink signal.

The PBCH carries information about the cell, comprising a masterinformation block (MIB) that includes parameters that LTE terminals useto properly access the cell. Data transmitted to terminals on thephysical downlink shared channel (PDSCH), which may also be referred toas a downlink data channel, can be transmitted in other resourceelements of the subframe. In general PDSCH conveys a combination ofuser-plane data and non-physical layer control-plane data (such as RadioResource Control (RRC) and Non Access Stratum (NAS) signalling). Theuser-plane data and non-physical layer control-plane data conveyed onPDSCH may be referred to as higher layer data (i.e. data associated witha layer higher than the physical layer).

FIG. 3 also shows a region of PDSCH containing system information andextending over a bandwidth of R344. A conventional LTE subframe willalso include reference signals which are not shown in FIG. 3 in theinterests of clarity.

The number of subcarriers in a LTE channel can vary depending on theconfiguration of the transmission network. Typically this variation isfrom 72 sub carriers contained within a 1.4 MHz channel bandwidth to1200 subcarriers contained within a 20 MHz channel bandwidth (asschematically shown in FIG. 3). As is known in the art, data transmittedon the PDCCH, PCFICH and PHICH is typically distributed on thesubcarriers across the entire bandwidth of the subframe to provide forfrequency diversity.

The communications between the base stations 101 and the terminaldevices 104 are conventionally made using radio resources that have beenlicensed for exclusive use by the operator of the network 100. Theselicensed radio resources will be only a portion of the overall radiospectrum. Other devices within the environment of the network 100 may bewirelessly communicating using other radio resources. For example, adifferent operator's network may be operating within the samegeographical region using different radio resources that have beenlicensed for use by the different operator. Other devices may beoperating using other radio resources in an unlicensed radio spectrumband, for example using Wi-Fi or Bluetooth technologies.

As noted above, it has been proposed that a wireless telecommunicationsnetwork using radio resources in a licensed portion of the radiospectrum might be supported by additionally using radio resources in anunlicensed portion of the radio spectrum (i.e. a portion of the radiospectrum over which the wireless telecommunications network does nothave exclusive access, but rather which is shared by other accesstechnologies and/or other wireless telecommunications networks). Inparticular, it has been proposed that carrier aggregation basedtechniques may be used to allow unlicensed radio resources to be used inconjunction with licensed radio resources.

In essence, carrier aggregation allows for communications between a basestation and a terminal device to be made using more than one carrier.This can increase the maximum data rate that may be achieved between abase station and a terminal device as compared to when using only onecarrier and can help enable more efficient and productive use offragmented spectrum. Individual carriers that are aggregated arecommonly referred to as component carriers (or sometimes simplycomponents). In the context of LTE, carrier aggregation was introducedin Release 10 of the standard. In accordance with the current standardsfor carrier aggregation in an LTE-based system, up to five componentcarriers can be aggregated for each of downlink and uplink. Thecomponent carriers are not required to be contiguous with one anotherand can have a system bandwidth corresponding to any of the LTE-definedvalues (1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz), therebyallowing a total bandwidth of up to 100 MHz. Of course it will beappreciated this is just one example of a specific carrier aggregationimplementation and other implementations may allow for different numbersof component carriers and/or bandwidths.

Further information on the operation of carrier aggregation in thecontext of LTE-based wireless telecommunications systems can be found inthe relevant standards documents, such as ETSI TS 136 211 V11.5.0 (2014January)/3GPP TS 36.211 version 11.5.0 Release 11 [2], ETSI TS 136 212V11.4.0 (2014 January)/3GPP TS 36.212 version 11.4.0 Release 11 [3];ETSI TS 136 213 V11.6.0 (2014 March)/3GPP TS 36.213 version 11.6.0Release 11 [4]; ETSI TS 136 321 V11.5.0 (2014 March)/3GPP TS 36.321version 11.5.0 Release 11 [5]; and ETSI TS 136 331 V11.7.0 (2014March)/3GPP TS 36.331 version 11.7.0 Release 11 [6].

In accordance with the terminology and implementation used for carrieraggregation in the context of an LTE-based system, a cell is denoted the‘primary cell’, or Pcell, for a terminal device if it is the cell thatis initially configured during connection setup for the terminal device.Thus the primary cell handles RRC (radio resource control) connectionestablishment/re-establishment for the terminal device. The primary cellis associated with a downlink component carrier and an uplink componentcarrier (CoC). These may sometimes be referred to herein as primarycomponent carriers. A cell that is configured for use by the terminaldevice after initial connection establishment on the Pcell is termed a‘secondary cell’, or Scell. Thus the secondary cells are configuredafter connection establishment to provide additional radio resources.The carriers associated with Scells may sometimes be referred to hereinas secondary component carriers. Since in LTE up to five componentcarriers can be aggregated, up to four Scells (correspondinglyassociated with up to four secondary component carriers) can beconfigured for aggregation with the primary cell (associated with theprimary component carrier). An Scell might not have both a downlink anduplink component carrier and the association between uplink componentcarriers and downlink component carriers is signalled in SIB2 via systeminformation on each downlink component carrier. The primary cellsupports PDCCH and PDSCH on downlink and PUSCH and PUCCH on uplinkwhereas the secondary cell(s) support PDCCH and PDSCH on downlink andPUSCH on uplink, but not PUCCH. The enhanced PDCCH (E-PDCCH) may be usedin addition to or instead of the PDCCH on both the primary and secondarycells. Measurement and mobility procedures are handled on the Pcell andthe Pcell cannot be de-activated. The Scell(s) may be dynamicallyactivated and deactivated, for example according to traffic needs,through MAC layer signalling to the terminal device. An Scell for aterminal device may also be deactivated automatically (time out) if theterminal device does not receive any transmission resource allocationson the Scell for a threshold amount of time.

Some aspects of physical layer control signalling for an LTE-basedimplementation of carrier aggregation based on the current standards arenow described.

Each downlink component carrier has the normal LTE control channels:(E)PDCCH, PCFICH and PHICH. However, carrier aggregation introduces thepossibility of so-called cross-carrier scheduling (XCS) on PDCCH. Tosupport cross-carrier scheduling, a downlink control information (DCI)message on PDCCH includes a carrier indicator field (CIF) comprisingthree bits to indicate which of the component carriers the PDCCH messageapplies to. If there is no CIF, the PDCCH is treated as applying to thecarrier on which it is received. A motivation for providingcross-carrier scheduling primarily applies for heterogeneous network(het-net) scenarios where overlaid macro- and small-cells may operatecarrier aggregation in the same band. The effects of interferencebetween the respective macro- and small-cells' PDCCH signalling can bemitigated by having the macro-cell transmit its PDCCH signalling on onecomponent carrier at relatively high transmit power (to provide coverageacross the macro-cell), while the small-cells use an alternativecomponent carrier for their PDCCH scheduling.

The control region supporting PDCCH may differ in size (i.e. number ofOFDM symbols) between component carriers, so they can carry differentPCFICH values. However, the potential for interference in the controlregion in a het-net implementation may mean that PCFICH cannot bedecoded on a particular component carrier. Therefore, current LTEstandards allow for each component to carry a semi-static indication ofwhich OFDM symbol PDSCH can be assumed to begin on in each subframe. Iffewer OFDM symbols are actually used for the control region, thefree/spare OFDM symbol(s) may be used for PDSCH transmissions toterminal devices which are not being cross-carrier scheduled as theywill decode the actual PCFICH. If more OFDM symbols are actually usedfor the control region, there will be some degree of performancedegradation for the cross-carrier scheduled terminal devices.

PHICH signalling is sent on the downlink component carrier that sent thePDCCH signalling containing the PUSCH allocation to which the PHICHsignalling relates. Accordingly, one downlink component carrier maycarry PHICH for more than one component carrier.

In the uplink, the basic operation of PUCCH is not altered by theintroduction of carrier aggregation. However, a new PUCCH format (format3) is introduced to support the sending of acknowledgement signalling(ACK/NACK signalling) for multiple downlink component carriers, and withsome alterations to format 1b to increase the number of ACK/NACK bits itcan carry.

In current LTE-based carrier aggregation scenarios, primary andsecondary synchronisation signalling (PSS and SSS) are transmitted onall component carriers using the same physical-layer cell identity (PCI)and component carriers are all synchronised with one another. This canhelp with cell search and discovery procedures. Issues relating tosecurity and system information (SI) are handled by the Pcell. Inparticular, when activating an Scell, the Pcell delivers the relevant SIfor the Scell to the terminal device using dedicated RRC signalling. Ifthe system information relating to a Scell changes, the Scell isreleased and re-added by Pcell RRC signalling (in one RRC message).Pcell changes, e.g. due to long-term fluctuations in channel qualityacross the Pcell bandwidth, are handled using a modified handoverprocedure. The source Pcell passes all the relevant carrier aggregation(CA) information to the target Pcell so the terminal device can begin touse all the assigned component carriers when handover is complete.

Random access procedures are primarily handled on the uplink componentcarrier of Pcell for a terminal device, although some aspects ofcontention resolution signalling may be cross-carrier scheduled toanother serving cell (i.e. an Scell).

As noted above, carrier aggregation is one approach for making use ofunlicensed radio spectrum resources in wireless communication networkswhich are primarily designed to use licensed radio spectrum. In broadsummary, a carrier aggregation based approach may be used to configureand operate a first component carrier (e.g. a primary component carrierassociated with a Pcell in LTE terminology) within a region of the radiospectrum that has been licensed for use by a wireless telecommunicationsnetwork, and to also configure and operate one or more further componentcarriers (e.g. a secondary component carrier associated with an Scell inLTE terminology) in an unlicensed region of the radio spectrum. Thesecondary component carrier(s) operating in the unlicensed region of theradio spectrum may do so in an opportunistic manner by making use of theunlicensed radio resources when they are available. There may also beprovisions made for restricting the extent to which a given operator canmake use of the unlicensed radio resources, for example by defining whatmight be referred to as politeness protocols.

Although known carrier aggregation schemes can form a basis for usingunlicensed radio spectrum resources (or other forms of shared radioresources) in conjunction with licensed radio spectrum resources, somemodifications to known carrier aggregation techniques may be appropriateto help optimise performance. This is because radio interference in theunlicensed radio spectrum can be expected to be subject to a wider rangeof unknown and unpredictable variations in time and frequency than mightbe seen within a region of the radio spectrum which has been licensedfor use by a particular wireless communications system. For a givenwireless telecommunications system operating in accordance with a giventechnology, such as LTE-A, interference in the unlicensed radio spectrummay arise from other systems operating substantially the sametechnology, or systems operating according to different technologies,such as Wi-Fi or Bluetooth.

FIG. 4 schematically shows a telecommunications system 400. Thetelecommunications system 400 in this example is based broadly on aLTE-type architecture. As such many aspects of the operation of thetelecommunications system 400 are standard and well understood and notdescribed here in detail in the interest of brevity. Operational aspectsof the telecommunications system 400 which are not specificallydescribed herein may be implemented in accordance with any knowntechniques, for example according to the established LTE-standards andknown variations thereof.

The telecommunications system 400 comprises a core network part (evolvedpacket core) 402 coupled to a radio network part. The radio network partcomprises a base station (evolved-nodeB) 404, a first terminal device406 and a second terminal device 408. It will of course be appreciatedthat in practice the radio network part may comprise a plurality of basestations serving a larger number of terminal devices across variouscommunication cells. However, only a single base station and twoterminal devices are shown in FIG. 4 in the interests of simplicity.

Although not part of the telecommunications system 400 itself, alsoshown in FIG. 4 are some other devices which are operable to wirelesslycommunicate with one another and which are operating within the radioenvironment of the telecommunications system 400. In particular, thereis a pair of wireless access devices 416 communicating with one anothervia radio link 418 operating in accordance with a Wi-Fi standard and apair of Bluetooth devices 420 communicating with one another via radiolink 422 operating in accordance with a Bluetooth standard. These otherdevices represent a potential source of radio interference for thetelecommunications system 400. It will be appreciated that in practicethere will typically be many more such devices operating in the radioenvironment of the wireless telecommunications system 400, and only twopairs of devices 418, 422 are shown in FIG. 4 for simplicity.

As with a conventional mobile radio network, the terminal devices 406,408 are arranged to wirelessly communicate data to and from the basestation (transceiver station) 404. The base station is in turncommunicatively connected to a serving gateway, S-GW, (not shown) in thecore network part which is arranged to perform routing and management ofmobile communications services to the terminal devices in thetelecommunications system 400 via the base station 404. In order tomaintain mobility management and connectivity, the core network part 402also includes a mobility management entity (not shown) which manages theenhanced packet service, EPS, connections with the terminal devices 406,408 operating in the communications system based on subscriberinformation stored in a home subscriber server, HSS. Other networkcomponents in the core network (also not shown for simplicity) include apolicy charging and resource function, PCRF, and a packet data networkgateway, PDN-GW, which provides a connection from the core network part402 to an external packet data network, for example the Internet. Asnoted above, the operation of the various elements of the communicationssystem 400 shown in FIG. 4 may be broadly conventional apart from wheremodified to provide functionality in accordance with examples of thedisclosure as discussed herein.

The terminal devices 406, 408 each comprise a transceiver unit 406 a,408 a for transmission and reception of wireless signals and acontroller unit 406 b, 408 b configured to control the operation of therespective devices 406, 408 in accordance with examples of thedisclosure. The respective controller units 406 b, 408 b may eachcomprise a processor unit which is suitably configured/programmed toprovide the desired functionality described herein using conventionalprogramming/configuration techniques for equipment in wirelesstelecommunications systems. For each of the terminal devices 406, 408,their respective transceiver units 406 a, 408 a and controller units 406b, 408 b are schematically shown in FIG. 4 as separate elements for easeof representation. However, it will be appreciated that for eachterminal device the functionality of these units can be provided invarious different ways, for example using a single suitably programmedgeneral purpose computer, or suitably configured application-specificintegrated circuit(s)/circuitry, or using a plurality of discretecircuitry/processing elements for providing different elements of thedesired functionality. It will be appreciated the terminal devices 406,408 will in general comprise various other elements associated withtheir operating functionality in accordance with established wirelesstelecommunications techniques (e.g. a power source, possibly a userinterface, and so forth).

As has become commonplace in the field of wireless telecommunications,terminal devices may support Wi-Fi and Bluetooth functionality inaddition to cellular/mobile telecommunications functionality. Thus thetransceiver units 406 a, 408 a of the respective terminal devices maycomprise functional modules operable according to different wirelesscommunications operating standards. For example, the terminal devices'transceiver units may each comprise an LTE transceiver module forsupporting wireless communications in accordance with an LTE-basedoperating standard, a WLAN transceiver module for supporting wirelesscommunications in accordance with a WLAN operating standard (e.g. aWi-Fi standard), and a Bluetooth transceiver module for supportingwireless communications in accordance with a Bluetooth operatingstandard.

The underlying functionality of the different transceiver modules may beprovided in accordance with conventional techniques. For example, aterminal device may have separate hardware elements to provide thefunctionality of each transceiver module, or alternatively, a terminaldevice might comprise at least some hardware elements which areconfigurable to provide some or all functionality of multipletransceiver modules. Thus the transceiver units 406 a, 408 a of theterminal devices 406, 408 represented in FIG. 4 are assumed here toprovide the functionality of an LTE transceiver module, a Wi-Fitransceiver module and a Bluetooth transceiver module in accordance withconventional wireless communications techniques.

The base station 404 comprises a transceiver unit 404 a for transmissionand reception of wireless signals and a controller unit 404 b configuredto control the base station 404. The controller unit 404 b may comprisea processor unit which is suitably configured/programmed to provide thedesired functionality described herein using conventionalprogramming/configuration techniques for equipment in wirelesstelecommunications systems. The transceiver unit 404 a and thecontroller unit 404 b are schematically shown in FIG. 4 as separateelements for ease of representation. However, it will be appreciatedthat the functionality of these units can be provided in variousdifferent ways, for example using a single suitably programmed generalpurpose computer, or suitably configured application-specific integratedcircuit(s)/circuitry or using a plurality of discretecircuitry/processing elements for providing different elements of thedesired functionality. It will be appreciated the base station 404 willin general comprise various other elements associated with its operatingfunctionality. For example, the base station 404 will in generalcomprise a scheduling entity responsible for scheduling communications.The functionality of the scheduling entity may, for example, be subsumedby the controller unit 404 b.

Thus, the base station 404 is configured to communicate data with thefirst and second terminal devices 406, 408 over respective first andsecond radio communication links 410, 412. The wirelesstelecommunications system 400 supports a carrier aggregation mode ofoperation in which the first and second radio communication links 410,412 each comprise a wireless access interface provided by multiplecomponent carriers. For example, each radio communication link maycomprise a primary component carrier and one or more secondary componentcarriers. Furthermore, the elements comprising the wirelesstelecommunications system 400 in accordance with this example of thedisclosure are assumed to support carrier aggregation in an unlicensedspectrum mode. In this unlicensed spectrum mode the base stationcommunicates with terminal devices using a primary component carrieroperating on radio resources within a first frequency band that has beenlicensed for use by the wireless telecommunications system and one ormore secondary component carriers operating on radio resources within asecond frequency band that has not been licensed for exclusive use bythe wireless telecommunications system. The first frequency band maysometimes be referred to herein as a licensed frequency band and thesecond frequency band may sometimes be referred to herein as anunlicensed (U) frequency band. In the context of an LTE-based wirelesstelecommunications system, such as that represented in FIG. 4, operationin the unlicensed frequency band may be referred to as an LTE-U mode ofoperation. The first (licenced) frequency band may be referred to as anLTE band (or more particularly an LTE-A band) and the second(unlicensed) frequency band may be referred to as an LTE-U band.Resources on the LTE-U band may be referred to as U-resources. Aterminal device able to make use of U-resources may be referred to as aU-terminal device (or U-UE). More generally, the qualifier “U” may beused herein to conveniently identify operations in respect of theunlicensed frequency band.

It will be appreciated that the use of carrier aggregation techniquesand the use of unlicensed spectrum resources (i.e. resources that may beused by other devices without centralised coordination) in accordancewith examples of the disclosure may be based generally on previouslyproposed principles for such modes of operation, for example asdiscussed above, but with modifications as described herein to provideadditional functionality in accordance with examples of the presentdisclosure. Accordingly, aspects of the carrier aggregation andunlicensed spectrum operation which are not described in detail hereinmay be implemented in accordance with known techniques.

Modes of operation for the wireless telecommunications network 400represented in FIG. 4 in accordance with certain examples of thedisclosure will now be described. The general scenario for theseexamples is assumed to be one in which a carrier aggregation capableterminal device is operating in an LTE-A cell as normal, and the basestation determines that it should configure the LTE-U capable terminaldevice with an additional aggregated carrier using LTE-U resources. Thespecific reason why the base station determines that it should configurea particular terminal device for LTE-U based carrier aggregation is notsignificant. Thus the LTE-A carrier provides a Pcell for the terminaldevice and the LTE-U resources provide one or more Scell(s) for theterminal device. It will be appreciated the LTE-A resources may also beused to provide component carriers associated with one or more furtherScells(s) in accordance with conventional carrier aggregationtechniques. For the examples described with reference to FIG. 4, theLTE-A transmissions in the licenced frequency band and the LTE-Utransmissions in the unlicensed frequency band, and thus the Pcell andScell(s), are both made from the same base station 404, but this may notbe the case in other examples. The LTE-U carrier could in general beutilised with a TDD (time division duplex) or FDD (frequency divisionduplex) frame structure. However, a consequence of some aspects ofexisting regulatory restrictions on unlicensed spectrum usage in someregions means that TDD or downlink-only FDD operation may, at leastcurrently, be more likely. Although the present disclosure is generallydescribed in the context of FDD, the same teachings apply equally to aTDD frame structure, and the skilled person would be able to apply theteachings of the present disclosure to such a TDD frame structure.

Accordingly, based on carrier aggregation techniques, unlicensedspectrum can be used in combination with licensed spectrum for thetransmission of data between terminal devices and base stations.However, the use of an unlicensed spectrum has a significant effect onresources planning and utilisation, in particular for MNOs.Conventionally, an MNO would only use a licensed spectrum, which is notshared with another party and would carry out drive tests to audit anarea in respect of coverage, signal power, interferences, performance,etc. to assess the coverage quality. Drive tests are conventionallycarried out using field engineers to manually collect measurement data.The collected data is then used by the MNO to adjust, if necessary, thenetwork configuration (e.g. frequency bands, transmission power, etc.)with a view to optimising the resource utilisation in the area.Recently, there has been discussion of using terminal devices to sendquality reports to the network with a view to avoiding traditional drivetests. The Minimisation of Drive Tests (MDT) is discussed in particularin 3GPP TS 37.320 [7], 3GPP TR 36.805 [8] and 3GPP TS 32.422 [9]. MDTdiscusses that terminal devices may be asked to collect data on thenetwork performance and to report on the measurement back to thenetwork.

While MDT can help simplify how the data is collected and reported tothe network by alleviating the need for field engineers to be deployedwhen quality data is to be collected, the network optimisation remainssignificantly facilitated by the fact that the frequency bands orchannels used are in a licensed spectrum. As a result, the transmissionswithin the network should only suffer from interferences from signalsfrom the same network, i.e. within the MNO's control. In contrast, whenusing unlicensed frequencies, interferences can be caused by any othertype of signals without the control of the MNO, such as Wi-Ficommunications, Bluetooth, near field communication (NFC) devices oreven microwave devices. In this situation, any spectrum and resourcesmanagement is significantly complicated and, essentially, conventionalspectrum management methods cannot provide the same results in anunlicensed spectrum than in a licensed—and thus controlled—spectrum.Additionally, the MNO is not in a position to plan for frequencyresources as the MNO cannot know in advance whether certain frequencyresources will be used or available for its transmission, contrary toresources in a licensed band. It is therefore desirable to facilitatefrequency planning for the MNO when using unlicensed spectrum.

In accordance with an example of the present disclosure, a terminaldevice may be operable to collect measurements and to obtain anindication of a channel occupancy level for an unlicensed frequencyband. The channel occupancy level for a period of time is estimatedbased on a channel occupancy state obtained for each of a set of shortertime periods within the period of time for the channel occupancy level.Accordingly, the terminal device can collect occupancy information inrespect of an unlicensed spectrum so as to form a view of whether thechannel is shared with many active devices (upon which the MNO haspotentially no control). Such an occupancy level as determined by theterminal device can be used for the network (e.g. base station) todecide whether an unlicensed frequency band may be used to transmitdata. Advantageously, such an occupancy level can provide the MNO withan indication of whether resources are likely to be available in thespectrum and thus of the likelihood of having successful transmissionsusing this spectrum. In view of the number of technologies and devicespotentially using the frequency band, the MNO may rely on moreopportunistic allocation mechanisms, rather than conventionally plannedresources allocations, such that an indication of an occupancy level foran unlicensed band provides a useful tool for the MNO to try to use thatunlicensed band.

FIG. 5 provides a schematic illustration of a channel occupancymeasurement. A channel occupancy state is measured for a short period“t” and provides an indication of the occupancy of the channel on thattime period t. In the example of FIG. 5, the state may be one of“occupied” or “free” but in other examples, more and/or different statesmay be used. A channel occupancy level is measured for a longer timeperiod “T”, wherein a plurality of short time periods “t” are within thelonger time period “T”. In this example, the long time period T is madeof 20 consecutive short time periods “t”, however in other examples, therelative short/long time period arrangement may be different, asdiscussed below. In the remainder of the description, the short period tand long period T may also be referred to as first and second (time)periods, respectively. FIG. 5 illustrates with graphic 500 the power 510(in dBm, ordinate) received by a transceiver depending on the time(abscissa). For example, an LTE transceiver may operate in a measurementmode when no LTE transmissions are scheduled and may measure all powerreceived in the unlicensed band. For each of the first periods, theterminal (e.g. the controller unit of the terminal) determines whetherthe band is occupied or free. This can be performed by comparing thereceived power 510 with a threshold 511. For example, if the power 510is above the threshold 511 for the entire duration of the period t, theband will be considered as occupied, otherwise it will be considered asfree. In other examples, for the band to be considered as occupied, thepower 510 will have to be above the threshold 511 for at least a portionp of the time period t, where p can for example be 50% or any suitablerange in the 1%-99% range. In other examples, the occupancy state may bedetermined based on the energy received for transmissions where thepower 510 is above threshold 511. This can be illustrated in the exampleof FIG. 5, with the second short period, where the power 510 is abovethe threshold 511. In this example, the area 520 (corresponding to theenergy for the transmission power above the threshold) may be calculatedor estimated when trying to determine the occupancy state for this shorttime period. This area 520 may then be compared with a second thresholdto estimate the band's occupancy state for this short period. Forexample, depending on the selected second threshold, in some cases itmay be considered that the band is occupied for the short periods number2-3 and 7-11 but not for the short periods 15-16.

In the example illustrated in FIG. 5, it is determined from the power511 received on the unlicensed band that the channel is occupied at theshort time periods number 2-3, 7-11 and 15-16 of time periods 1-20 (e.g.based on a power 510 being above the threshold 511 for at least aportion p=80% of the short time period). The band is thus considered asoccupied for nine (9) of the short time periods and the occupancy levelderived from this can for example be calculated as 9/20=45%. Such anoccupancy level provides an indication of how much the band is used byother parties and an MNO can thus make use of this information whenplanning resources allocation. The MNO could also use this informationwhen deciding whether to use the band for a secondary carrier and/or howmuch data it should be able to send through this secondary carrier basedon the occupancy level reports it has received from terminal devices.

FIG. 6 provides a schematic flowchart of a method of measuring and ofreporting occupancy. In this example, a terminal device 406, 408 hasdual wireless capabilities with WLAN and LTE capabilities, and measuresan occupancy level on an unlicensed channel which may also be used byWLAN technologies. In the example of FIG. 6, the terminal device firstreceived the measurement request from the eNB at S601. Upon reception ofthe request, the terminal device measures the WLAN occupancy using itsWLAN module at S603. For example the WLAN module can monitor the WLANtransmissions in the unlicensed band. At step S605, the terminal devicemeasures the LTE channel occupancy using the LTE module and combines themeasurements results from the LTE module with the measurements resultsfrom the WLAN module. In a first example, the specific measurementresults may be combined by generating global measurement results whichincludes both LTE and WLAN measurement results, separately. In a secondexample, they may be combined by processing the measurement results forWLAN and LTE to generate global measurement results which providesmeasurement data derived from WLAN and LTE measurements. For example, ifit is estimated that there is an overlap between LTE and WLANmeasurements, measurement data can be derived from this, for instance togenerate additional measurement data. For example, global measurementresults may be generated which can include LTE measurement results, WLANmeasurement results and estimated non-LTE and non-WLAN measurementresults wherein the latter is derived from the WLAN and LTE measurementresults.

As an illustration, if at a point in time in a specific frequency band,both the LTE and WLAN transceivers estimate a received power at thevalue “P” while the LTE and WLAN transceiver each estimates that, withinP, the LTE received power is P_(L) and the WLAN received power is P_(W),respectively, the two examples above could for example result in:

-   -   First example: the global measurements include the WLAN and LTE        measurements, separately. For example, it may include an        indication that the WLAN transceiver received P_(W) and P as        WLAN and total power, respectively and that the LTE transceiver        received P_(L) and P as LTE and total power, respectively.    -   Second example: the global measurement may optionally include        the same measurements as in the first example, and additional        measurements as follows: derived measurements may include an        indication that at that point in time P power was received in        the frequency band, including P_(L) for LTE communications,        P_(W) for WLAN communications and (P-P_(L)-P_(W)) for        non-LTE/non-WLAN communications.

In the example of FIG. 6, the WLAN measurements and the LTE measurementsare shown as being performed sequentially however, in other examples,these measurements may be carried out in a different order or may becarried out in parallel. Then, at step S607, the terminal device sends areport on the measured occupancy to the eNB 404. In this example, theWLAN occupancy measurements may help estimating whether there is anactive WLAN network in the area, i.e. active transmissions in the sharedband from different technologies, while the LTE occupancy measurementsmay help estimating whether other mobile networks are using the sharedband for LTE transmissions. Based on a combination of the occupancymeasurements, the terminal device 406, 408 can generate an occupancyreport based on third parties' transmissions in the shared band usingthe WLAN and LTE technologies. In some examples, the report may indicatean overall channel occupancy for the unlicensed band regardless of thetechnology. In other examples, the report may indicate a channeloccupancy for the unlicensed band taking into account the technology.Such a report may for example show a 10% occupancy for WLAN and a 50%occupancy for LTE. It is noteworthy that the report may includeoccupancy levels with and without taking into account the technology ofthe transmissions. For example, a report may show an overall 40%occupancy, a 30% occupancy for WLAN and a 20% occupancy for LTE (if forexample WLAN only is active for 20% of the time, LTE only is active for10% of the time and both LTE and WLAN are active for 10% of the time).

Thus, the terminal device makes measurements of radio usage in theunlicensed frequency band in its environment. In particular, theterminal device measures the degree of radio usage at differentfrequencies across the second frequency band. For example, the terminaldevice may use its WLAN transceiver module to scan for activityassociated with other wireless communication devices, for example, Wi-Fiaccess points. From this the terminal device may establish, for example,an indication of frequency resources used by other wirelesscommunications devices and/or an indication of a received signalstrength for wireless communications associated with other wirelesscommunications devices and/or an indication of an identifier for theother wireless communications device (e.g. SSID). The terminal devicemay also scan for radio usage in the second frequency band by otherdevices operating according to other operating standards, for exampleBluetooth and/or other LTE networks. In some examples the terminaldevice might not separately measure radio usage by differenttechnologies, but may simply measure an aggregate level of radio signals(which may include radio noise) in its environment at differentfrequencies across the unlicensed frequency band. The terminal devicethen transmits an indication of the measurements of radio usage atdifferent frequencies across the second frequency band to the basestation. This may be done on uplink radio resources on thealready-configured primary cell to which the terminal device isconnected in accordance with conventional signalling techniques, forexample in accordance with the established principles of measurementreport RRC signalling, or on other uplink radio resources.

In the examples above, the indication of the channel occupancy isgenerally for signals on the channel which are not signals to or fromthe base station. They are instead signals transmitted by other wirelesscommunications systems, such as a WLAN network, Bluetooth systems oranother LTE system (e.g. made by another MNO). In other words, thechannel utilisation measured on the shared channel is preferably fortransmissions other than transmissions with the base station or themobile network of the terminal device. This is with the view toestimating the utilisation of the shared channel by other wirelesssystems which may affect the energy transmissions of the LTE network. Asmentioned in the present disclosure, the shared channel is used by otherparties over which the MNO has no control which makes any interferenceavoidance scheme much more complex than in the conventional mobilenetwork situation. However, various MNOs may decide to work together toreduce the interferences caused by their respective LTE transmissions inthe shared channel. The LTE transmissions in an unlicensed channel or ina shared channel would still be vulnerable to interferences with othertransmissions in the same frequency band however the level ofinterferences between LTE transmissions from different mobile networkscould be reduced. By agreeing on improving the sharing of the sharedchannel, the MNOs could improve the quality and or success rate of theirown transmissions in this shared channel. In the event that two (ormore) mobile network operators agree to a form of sharing scheme for thetransmission on the shared channel, it may be beneficial to obtain anindication of the channel utilisation level which excludes the LTEtransmissions from the friendly MNO. With a view to addressing thissituation, and in accordance with the present disclosure, there can beprovided a quiet time for the MNOs to obtain indications of the channeloccupancy level for other technologies and for non-friendly MNOs.

FIG. 7 provides a schematic time diagram showing an example use of aquiet time. In this example, the transmissions from a first mobileoperator MNO-A are shown in timeline 710, while transmissions from asecond mobile operator MNO-B are shown in timeline 720. The twooperators have agreed on a common quiet time during which they both stoptransmitting LTE signals. Thus the first operator MNO-A transmitssignals 711 before the quiet time, then stops transmitting during quiettime 712, and resumes transmissions once the quiet time is over bytransmitting signals 713. Likewise, the second operator MNO-B transmitssignals 721 before the quiet time, then stops transmitting during quiettime 722, and resumes transmissions once the quite time is over bytransmitting signals 723. Accordingly, both mobile operators can carryout occupancy levels monitoring during the quiet times and thereby avoidbeing affected by each other's LTE transmissions when they survey theshared channel. Even though the operators' transmissions in timelines710 and 720 have been represented as blocks, this is a simplificationfor the purpose of illustrating the use of quiet time, and it isunderstood that the base stations may not been transmitting signals forthe entire time periods for blocks 711, 713, 721 and 723. For example,as a result of a sharing scheme between the two operators, only one ofthe two operators may be transmitting at point in time. For example,operator MNO-A may be transmitting signals during period 711 but notduring period 713 while operator MNO-B may not be transmitting signalsduring period 721 but may be transmitting signals during period 723.

FIG. 8 provides a schematic time diagram showing another example use ofquiet times. In this example, timeline 810 illustrates activetransmission times for a first operator MNO-A and timeline 820illustrates active transmission times for a second operator MNO-B. Thetwo operators have agreed on a common quiet time which corresponds toquiet time 814 for MNO-A and to quiet time 824 for MNO-B. However theoperators each also have a respective quiet time during which the otheroperator may be transmitting signals on the shared channel. As a result,operator MNO-A can transmit signals during times 811, 813 and 815 butwill stop transmissions during quiet times 812 and 814 while operatorMNO-B can transmit signals during times 821, 823 and 825 but will stoptransmissions during quiet times 822 and 824. During quiet time 812,MNO-A can obtain an indication of the occupancy level for the sharedchannel including transmissions from the other operator and it canobtain an indication of the occupancy level without transmissions fromthe other operator during quite time 814. The same teachings apply tothe corresponding quiet times 822 and 824 of timeline 820 in respect ofoperator MNO-B.

In the discussions above, the measurements carried out by a UE aregenerally carried out while its mobile network is not transmitting. Suchan arrangement can be helpful for determining an indication of anoccupancy level of the shared channel based on all transmissions but forthe ones from the UE's mobile network. This is because these signals(the signals from a network that is not the UE's mobile network) are theones that may cause interferences with LTE signals from the UE's mobilenetwork, should the mobile network decide to use a secondary carrier onthe shared channel. Such an arrangement can also simplify the amount ofprocessing required for occupancy measurement as any signal received bythe transceiver in the frequency band being surveyed is a potentialinterferer signal. However, in accordance with the present disclosure,the occupancy measurements may also be carried out while the UE's mobilenetwork is transmitting signals to the UE.

FIG. 9 provides a schematic illustration of another channel occupancymeasurement where different measurement methods may be employeddepending on whether the UE is receiving LTE signals from the basestation or not. In the graph 900, the line 920 (the thicker line)represents LTE signals sent via the secondary carrier on the sharedchannel while line 910 (the thinner line) represent other signals in theshared channel, i.e. potential interferer signals, that have beenidentified by the UE. While the LTE network is using the shared channel,the UE can measure the Reference Signal Received Quality (RSRQ) so as toobtain an indication of the level of the signal quality in the channelduring the transmissions from the UE's mobile network, and may measurethe Received Signal Strength Indicator (RSSI) when the base station isnot sending LTE signals via the shared channel. The RSRQ is based on theReference signal receive power (RSRP) which is for LTE only and the RSSIwhich includes interference signals. Accordingly, the UE can obtain anindication of the occupancy level on the channel in situations where themobile network is actively sending signals to the UE and in situationswhere it is not actively sending signals to the UE. In this example, theLTE network starts using the shared channel from the second short periodand, at the fifth short period, an interferer signal is transmitted onthe same channel. This can be identified using the RSRQ measurement (orany other type of measurement indicating an interference levelidentified for the signals transmitted by the base station on the sharedchannel). When the LTE-U is inactive (e.g. from the short time periods 6to 13) the UE can use the RSSI measurement or any other type ofmeasurement indicating a power received via the shared channel to obtainan indication of the occupancy levels on the shared channel. In theexample of FIG. 9:

-   -   during the short time periods 1, 7, 10 to 13, 19 and 20 the        shared channel is considered as being free based on RSSI or        RSSI-like measurements,    -   during the short time periods 6, 8, 9, 17 and 18 the shared        channel is considered as being occupied based on RSSI or        RSSI-like measurements    -   during short time periods 2 to 4, 14 and 15 the shared channel        is considered as being free based on RSRQ or RSRQ-like        measurements and    -   during short time periods 5 and 16 the shared channel is        considered as being occupied based on RSRQ or RSRQ-like        measurements.

In this example, the terminal device can thus determine that the sharedchannel is estimated as being free for 13 of the 20 short time periodsand as being occupied for 7 of the 20 short time periods. Therefore theoccupancy level is estimated at 7/20=35%. This 35% estimation providesan indication of the occupancy level of the shared channel for the longtime period T.

Accordingly, the measurements for determining an occupancy state orlevel of the shared channel may be based on information obtained fromthe LTE module only and/or may be based on information obtained whilethe mobile network is transmitting signals via the shared channel.

The channel occupancy levels discussed in the present disclosureprovides an additional type of information when surveying the sharedchannel (compared to existing LTE channel surveying arrangements)wherein this information is suitable for opportunistic data schedulingin LTE-U. The network can use the occupancy information to estimatewhether the channel can be used for sending data and, if so, how much(in time) of the channel may be available for sending the data. Forexample this information may be used when deciding whether to set up anLTE-U secondary cell as discussed in the present disclosure.Additionally, the occupancy information may be used when an LTE-Usecondary cell is already active when monitoring the quality in thiscell. This occupancy information may also be linked to the location ofthe UE which reported the information so that the network can build anoverall view of the network based on different reports UEs and/or from aUE sending reports from different locations. The network may also useadditional information when building this view from the reports such asthe time of day, day of week, other time aspects, interferer signals'technology, etc.

FIG. 10 is a signalling ladder diagram schematically representing modesof operation for one of the terminal devices (UEs) 406, 408 and the basestation (eNB) 404 schematically represented in FIG. 4, illustratingexample situations where it may be desirable to obtain an indication ofan occupancy level of the shared channel from one or more UEs. Theoperation is for communicating using a primary component carrier(associated with a primary cell) operating on radio resources within afirst frequency band and a secondary component carrier (associated witha secondary cell) operating on radio resources within a second frequencyband. As discussed above, the first frequency band is taken tocorrespond with resources that have been licensed for dedicated use bythe operator of the wireless telecommunications system 400 whereas thesecond frequency band is taken to correspond with resources that areshared by other wireless communication technologies, and in particularin this example by Wi-Fi. In broad summary, a plurality of transmissionresource configurations (e.g. frequencies) can be established that mightpotentially be used for a secondary carrier in the context of carrieraggregation using radio resources that are shared between differentnetwork operators and/or different wireless access technologies, and itcan be indicated to a terminal device which configuration is to be usedin association with an allocation of transmission resources on thesecondary carrier.

Some aspects of the operation represented in FIG. 10 are performed in agenerally iterative manner as discussed further below. Processing asschematically represented in FIG. 10 is shown starting from a stage atwhich the terminal device is configured for operation on the primarycell associated with the primary carrier, but is not yet configured foroperation on the secondary cell associated with the secondary carrier.This may be, for example, because the terminal device has only justconnected to the primary cell or because a previous secondary cellconfiguration is no longer valid.

In step T1 the base station establishes a measure of radio usage in thesecond frequency band. In some example implementations the base stationmay itself measure radio usage at different frequencies across thesecond frequency band, but in this example it is assumed the terminaldevice makes these measurements and reports them to the base station.That is to say, in this example implementation the base stationestablishes radio usage across the second band (unlicensed band) fromreports received from the terminal device (and/or other terminal devicesoperating in the wireless telecommunications system). Based on themeasurement information regarding radio usage in the second frequencyband received from the terminal device, the base station establishesradio usage across the secondary band in step T1 represented in FIG. 10.

In step T2 the base station determines a plurality of potentialtransmission resource configurations, e.g. a plurality of potentialcarrier frequencies and bandwidths, for a secondary component carrieroperating in the second frequency band. This determination is based onthe radio usage established in step T1. For example, the base stationmay be configured to determine four (or another number) of possiblefrequency configurations (e.g. in terms of centre frequency and/orbandwidth) for a secondary component carrier operating within the secondfrequency band. These may be selected to correspond with regions of thesecond frequency band determined to have the lowest amount of radiousage according to usage established in step T1. For example, if thesecond frequency band supports Wi-Fi and Bluetooth communications byother wireless communication devices operating in the radio environmentof the terminal device, the base station may identify regions of thesecond frequency band which are expected to suffer least frominterference from such communications. For example, regions of thesecond frequency band spectrum where the measurements of radio usageestablished in step T1 indicate there is relatively little radio trafficthat would interfere with LTE-based communications between the basestation and the terminal device. More generally, the base station maydetermine appropriate transmission resources (e.g. in terms of timeand/or frequency resources) from within the second frequency band todefine a plurality of potential configuration settings for a secondarycomponent carrier based on the radio usage, including for example one ormore occupancy reports in accordance with the present disclosure,determined in step T1 using established techniques for selectingappropriate transmission resources in a competitive (opportunistic)radio environment when taking account of measurements of existing usage.For example, the base station may avoid using resources in regions ofthe second frequency band for which the terminal device measurementreports indicate a relatively high degree of radio usage, and mayinstead preferentially select configurations for the secondary carrierthat make use of transmission resources in spectral regions having arelatively low degree of radio usage.

In this particular example it is assumed the base station is configuredto select four potential configurations for a secondary carriercorresponding to the configurations identified as having the lowestexpectation of interference. In some cases account may also be taken ofthroughput. For example, a larger bandwidth that encompasses sub-regionsof the second frequency band having relatively high radio usage maynonetheless be selected over a smaller bandwidth that avoids thesub-regions associated with relatively high radio usage to avoidrestricting transmissions on the secondary carrier to a relativelynarrow bandwidths. In some cases the base station may also take intoaccount its own load, for example some carriers may already have beenassigned to other devices to operate using LTU-U.

For this particular example it is assumed step T2 results in thedetermination of four possible configuration settings, for example interms of carrier frequencies and/or carrier bandwidths, which mightsubsequently be used for secondary carrier operation. The differentsecondary carrier configuration settings may be contiguous ornon-contiguous across the second frequency band and may have the same ordifferent bandwidths. For example, the base station may determine thefollowing four potential configuration settings: Configuration 1=abandwidth of 5 MHz centred on a frequency of F1; Configuration 2=abandwidth of 10 MHz centred on a frequency of F2; Configuration 3=abandwidth of 10 MHz centred on a frequency of F3, Configuration 4=abandwidth of 20 MHz centred on a frequency of F4, where F4=F3+15 MHzsuch that Configuration 3 and 4 relate to contiguous frequencyresources. However, it will be appreciated this is simply one particularexample of what might be determined to be an appropriate group ofpotential configuration settings for a secondary carrier. In particular,in accordance with other implementations, there may be more or fewerpotential configuration settings determined in step T2, and furthermorethese configuration settings may be subject to restrictions according tothe implementation at hand. For example, if a particular implementationallows only a discrete number of bandwidths and/or frequencies for asecondary component carrier (e.g. according to a relevant operatingstandard for the wireless telecommunications system), this willcorrespondingly restrict the potential carrier configurations that mightbe determined in step T2. Thus, in the example of FIG. 10, a pluralityof potential configuration settings are determined for a secondarycomponent carrier operating in the unlicensed spectrum

In step T3 the base station provides the terminal device with anindication of the potential configuration settings. This may be done ondownlink radio resources on the already-configured primary cell inaccordance with conventional signalling techniques, for example inaccordance with the established principles of radio bearer(re)configuration message RRC signalling. The information transmitted instep T3 represents a plurality of potential transmission resourceconfiguration settings as established in step T2.

In step T4 the terminal device begins measuring channel quality for thesecondary carrier configured according to the different potentialconfigurations. The measurements of channel quality for the secondarycarrier may be based on example measurement methods discussed in thepresent disclosure and may also additionally be combined withestablished channel quality measurement techniques in wirelesstelecommunications systems. For example, the measurements undertaken instep T4 may include measurements in accordance with the discussion ofFIG. 5 above and measurements undertaken for conventional channelquality indicator (CQI) reporting in LTE wireless communication systems.The terminal device may sequentially configure its transceiver inaccordance with the different potential configuration settings receivedin step T3 and undertake channel quality measurement for each secondarycarrier configuration in turn based on conventional CQI reportingtechniques. The quality measurement carried out for each of theconfigurations may include conventional LTE quality measurementindication(s) and/or an additional indication of the occupancy level forthe frequencies corresponding to the configurations. If for example thedifferent configurations use different frequency bands, the channelquality measurement for a configuration may involve only obtaining anindication of the occupancy level for the relevant frequency band. Instep T5 the terminal device communicates an indication of the channelquality measurements to the base station.

It will be appreciated steps T4 and T5 are shown as separate steps inFIG. 10 for ease of representation. In practice it may be expected thatsteps T4 and T5 will be performed iteratively for each configurationsetting in turn as the terminal device hops through the potentialconfiguration settings. That is to say, the terminal device mayconfigure its transceiver in accordance with the first one of thepotential configuration settings, and then measure and report channelconditions for this configuration setting, and then reconfigure itstransceiver in accordance with a second one of the potentialconfiguration settings, and then measure and report channel conditionsfor this configuration setting, and so forth until channel qualityreports have been provided to the base station for a secondary carrieroperating in accordance with each of the potential configurationsettings. However, in another example implementation, and depending onthe terminal device's transceiver capabilities, the channel qualitymeasurement and reporting may be performed in parallel for multipleconfiguration settings.

Step T6 is performed when the base station is ready to schedule thetransmission of some data to the terminal device on the secondarycarrier. The nature of the data, and the reason why it needs to betransmitted, may not be significant. Based on the channel qualityreports received in step T5, the base station selects one of theplurality of potential configuration settings for a secondary carrier touse for transmitting the data to the terminal device. In this regard thebase station may, for example, choose the configuration setting which isassociated with the best channel conditions, as reported in step T5.When deciding what the best channel conditions may be, the base stationcan take into account parameters such as link quality and expectedtransmissions from third parties on the secondary carrier. In additionto selecting what is considered to be the most appropriate configurationsetting for the secondary component carrier based on the channel qualityreports, the base station also selects resources within the secondarychannel to use for communicating the data to the terminal device. Thesemay be selected in accordance with generally conventional schedulingtechniques in wireless telecommunications systems, for example takingaccount of the channel quality reports for the relevant carrierconfiguration. In some examples, the base station may decide not to usethe secondary carrier, for example if a sufficient channel qualitycannot be achieved due to poor link quality or an expected high-level ofoccupancy for the secondary channel.

Step T6 may be executed in response to the terminal device havingreported a measurement on one or more of the potential configurationsthat indicates that the potential configuration is suitable for use as asecondary carrier. For example, if in step T5 the terminal deviceiteratively reports on the potential configurations and the measurementreport from the first potential configuration is deemed to be ofsufficient quality, the selection in step T6 may choose the firstpotential configuration and the terminal device does not need to performiterative measurements on the second, third and fourth potentialconfigurations.

In step T7 the base station transmits a resource allocation message tothe terminal device indicating the resources within the secondarycarrier that are scheduled (allocated/granted) for use by the terminaldevice. The resource allocation message regarding the allocation ofresources within the secondary carrier may be based on conventionaltechniques, for example in an LTE context the message of step T7 may beprovided as downlink control information (DCI) signalling on (E)PDCCH inorder to indicate transmission resources on PDSCH according to generallyconventional techniques. Furthermore, the resource allocation messagerelating to the secondary carrier may be communicated on the primarycarrier in accordance with established cross-carrier schedulingtechniques in carrier aggregation scenarios. In the example of FIG. 10,the resource allocation message indicating the allocation of resourceswithin the secondary carrier is additionally associated with anindication of the configuration setting selected by the base station instep T6 for configuring the secondary carrier for transmitting the datato which the resource allocation message relates.

In step T8 represented in FIG. 10, the base station proceeds tocommunicate data to the terminal device on a secondary component carrierconfigured in accordance with the selected configuration setting, andusing transmission resources within the secondary component carrier asidentified by the resource allocation message. The terminal device isable to configure its transceiver in accordance with the selectedconfiguration setting for the secondary carrier and decode the relevanttransmission resources to receive the data.

For implementations in which the indication of the selected carrierconfiguration is provided in the same subframe (time block) as the datato which the resource allocation message relates (for example within acontrol region of the subframe, e.g. within the (E)PDCCH resourceallocation message itself in an LTE-based implementation), the terminaldevices may receive and buffer radio signals on transmission resourcesassociated with all the potential carrier configurations so theappropriate transmission resources can be decoded once the selectedconfiguration setting is established by the terminal device from thesignalling received from the base station. In other implementations inwhich the indication of the selected carrier configuration is providedin advance of the subframe containing the data to which the resourceallocation message relates, the terminal device may configure itstransceiver for receiving the secondary carrier in accordance with theselected configuration settings to allow the allocated resources to bedecoded.

After the data is communicated in step T8, the processing may return tostep T4 and continue from there in an iterative manner.

Variations, Alternatives and Modifications

In the above discussions, the determination of a state (or of anestimated state) as observed by a terminal is based on the powerreceived by a receiver (e.g. in a transceiver) and on whether the poweris above a threshold, for example for at least a certain portion p ofthe time period in question. However, other types of comparisons may bemade with the threshold. For example, the average power during the shorttime period t; the median power during this period; the power atspecific point in time within the period (e.g. the power received at thebeginning, at the end, in the middle of the period), the minimum ormaximum power during the time period or any other identifiable value maybe compared with the threshold. Alternatively or in addition, the energyreceived during the time period may also be compared for apre-determined value, wherein the energy may be for power above areference power (e.g. in the example of FIG. 5 the energy identifiedwith area 520 corresponds to power 510 above threshold 511 which servesas a reference power for the purpose of calculating the energy).Therefore, for the purpose of estimating an occupancy state, the“energy” value calculated may be of a negative value (e.g. in theexample of FIG. 5, if the energy for power above the threshold 511 iscalculated for the fourth short period, the value obtained would benegative). It can thus be understood from this example that the valuescalculated, estimated and/or derived from channel utilisationmeasurements may be artificial values generated or estimated for thepurpose of obtaining an indication of an occupancy state of the channelduring the relevant short time period.

Also, these different mechanisms for determining an occupancy state maybe combined in any appropriate manner. For example, a minimum receivedpower may be compared with a first threshold while an average power maybe compared with a second threshold and while the energy fortransmissions above a third power threshold is compared with a fourth(energy) threshold.

Also, In the examples above, an occupancy state (corresponding to ashort period of time t) has been mostly described as being eitheroccupied or free. However, in other examples different states may beconsidered. For example there could be provided a “partial” state whenthe signal has been identified but is not very strong. For example therecould be provided two thresholds: a lower threshold “I1” and higherthreshold “I2”.

Using the teachings discussed in respect of FIG. 5 above, for signalsunder the lower threshold I1, the channel may be considered as free; forsignals between the lower threshold I1 and higher threshold I2, thechannel may be considered as partial; and for signals above the higherthreshold I2, the channel may be considered as occupied. As discussedabove further considerations may be taken into account when estimatingan occupancy state, such as the relative portion of each state duringthe short time period t, the energy received during the short timeperiod t and above one or both of the lower and higher thresholds, etc.

In other examples, the occupancy state may be represented by a numberbetween 0 and 1 where 0 represents the channel believed to be free and 1represents the channel believed to be occupied. A state estimated to bevalued at 0.1 for example can indicate that a very low level oftransmissions has been identified while a state estimated to be valuedat 0.8 can indicate a high level of transmissions in the shared channel.The value for a short time period “t” can be determined using anyappropriate estimation mechanism: for example, if all transmissionsremain under a threshold I0, the value is set to 0, for alltransmissions above a higher threshold I1, the value is set to 1, andfor transmissions between thresholds I0 and I1, the values can bedistributed from 0 to 1 in a suitable manner, for example linearly or ina non-linear way. When deciding how the transmissions compare with thethreshold(s), the same aspects can be considered as discussed above(e.g. taking into account the average, median, minimum, etc.).

Regardless of the occupancy states having two or more possible values,the occupancy level for the corresponding time period (the longer timeperiod T=20×t in the illustrations of FIGS. 5 and 9) may be calculatedbased on a suitable method, for example by calculating an average (asillustrated in FIGS. 5 and 9 where the channel occupancy percentage canalso be viewed as an average across period T of the channel beingoccupied “1” or free “0” during the short periods) or a weighted sum.For example each state may be given a weight depending on otherparameters, e.g. on a confidence level reflecting the confidence in theoccupancy state value previously estimated.

It is pointed out that the thresholds or other parameters to be used inaccordance with the present disclosure may be set in any appropriatemanner. They can for example be pre-determined or configurable by thebase station, another network element, the terminal device and/or theuser. They may also be set by the network which then transmits therelevant parameters to the terminal devices via the base station. Also,some parameters—and in particular time parameters—may include randomcomponents if appropriate. For example, idles UEs may be configured tocarry out the next measurements after a timer T_(next) has expired,where T_(next) may include a fixed component T_(min), which correspondsto the minimum waiting time between two measurements, and a randomcomponent T_(ran). Due to the random component, different UEs would belikely carry out measurements at different times and to (possibly) sendcorresponding reports at different times. As a result, the mobilenetwork would be likely to receive reports which are spread out andwhich correspond to different time periods. This would in turn bebeneficial with a view to building a more complete view of the occupancylevels and to spreading the measurement report traffic in time.

In the discussion above, the long time period (for estimating anoccupancy level) is made of 20 consecutive short time periods (forestimating an occupancy state). However the relative short/long timeperiod arrangement may be different. For example, the long time periodmay include fewer or more short time periods, for example it may include10 short time periods or 30 short time periods. Also the short timeperiods within the long time period may not be consecutive and some orall of them may be spaced apart in time. For example, in each long timeperiod, a certain number of short time periods may be selected randomlyso that the entire long time period may not be surveyed but the networkmay form a view from a number of such reports as to the occupancy thatthe terminal devices may experience if transmitting at random times.

As mentioned, the occupancy level estimated by the terminal device is inrespect of a shared frequency band. In the case that one or more sharedbands may be used or that sub-frequencies within the band may be used,an occupancy level may be estimated for each of the relevant frequencyor sub-frequency bands. Accordingly, an occupancy report from theterminal device to the network may be separated out into occupancylevels for different sub-frequencies within a frequency band or fordifferent frequency bands to be surveyed. In the case of sub-frequencybands, the report may also include an indication of the occupancy levelfor the frequency band as a whole (comprising the sub-frequency bands).In accordance with the present disclosure, a terminal device may carryout an occupancy level estimation in one or more of the following cases:(1) It can be estimated periodically, for example in accordance with anew repetition period or with an existing one, e.g. the CQI measuring orreporting period; (2) it can be estimated upon receipt of a measurementrequest, for example as discussed in respect of FIG. 10; (3) It can beestimated at a randomly selected time or when one or more predeterminedevents occur. For example, a terminal device may be configured to carryout occupancy measurements upon request from the network (e.g. from thebase station) and, while the terminal device is in idle mode or in a lowactivity mode, at randomly selected times. In this manner, differentterminal devices would normally carry out measurements either whenrequested to do so, or at statistically different times from the otherterminals in the area (due to the random component) while the device hasa low activity (thereby avoiding using processing resources on thedevice when they are required for other tasks). Other predeterminedevents can include a mobile communications device being powered up, amobile communication device experiencing congestion on a frequencychannel, a user request, a mobile communications network request, theexpiry of a timer and a mobile communication device having a lowutilisation level.

Likewise, a terminal device may carry out an occupancy level estimationreporting procedure in one or more of: periodically, upon receipt of ameasurement report request, at a randomly selected time or when one ormore predetermined events occur. Additionally, the terminal device mayreport an occupancy level when the level is above a certain threshold.For example, the terminal device may determine an indication of anoccupancy level on a periodical basis but without automaticallyreporting the occupancy level to the base station. However, when theoccupancy level estimated on this periodical basis is found to be abovea certain threshold, the terminal device may then generate a reportingincluding (at least) this occupancy level and transmit the report to thenetwork, for example via the base station. Accordingly, terminal devicesmay carry out silent monitoring of possible interferences in thesecondary channel and may only use resources for reporting the estimatedoccupancy levels when they are found to be high, thereby indicating apossible congestion on the secondary channel. Alternatively the terminaldevice may monitor for low occupancy level and when the occupancy levelis below a threshold, report this to the base station so that the basestation is aware that the secondary channel may be or become availablefor use.

In accordance with the present disclosure, a report sent to the networkand/or base station includes at least the indication of the occupancylevel determined by the terminal device and can also include additionalinformation. For example, it may include an indication of occupancylevel for one or more previous (longer) periods, measurement data, anindication of one or more technologies which have been identified asactive in the relevant (longer) periods, location information, deviceidentity information, etc. The network may then use reports receivedfrom terminal devices for building an overall view of the transmissionswhich may cause interference depending on parameters such as, location,time, technology, frequency or sub-frequency band, etc.

In the present disclosure, when a mobile communication ortelecommunications system is carrying out a step or providing a feature,one or more elements of the system may be carrying the step providingthe feature. For example, a decision to activate or deactivate asecondary carrier may be taken at a base station and/or at a corenetwork element. Examples of element of the mobile system include forexample a base station, a MME or a S-GW.

Even though in the examples above, the UEs described may include morethan one transceiver (for example a WLAN and an LTE transceiver), thepresent disclosure is also applicable to a UE having only onetransceiver (for example an LTE transceiver only). For example, theexamples illustrated in FIGS. 7-8 can be implemented with a LTEtransceiver only. The other examples in the present disclosure may alsobe either be directly be implemented with a LTE transceiver only or maybe adapted to be implemented with a LTE transceiver only.

Elements are schematically shown in FIGS. 1 and 4 as separate elementsfor ease of representation. However, it will be appreciated that thefunctionality of these elements can be provided in various differentways, for example using a single suitably programmed general purposecomputer, or suitably configured application-specific integratedcircuit(s)/circuitry, or using a plurality of discretecircuitry/processing elements for providing different elements of thedesired functionality. It will be appreciated the elements will ingeneral comprise various other elements associated with their operatingfunctionality in accordance with established wireless telecommunicationstechniques (e.g. a power source, possibly a user interface, and soforth).

Further particular and preferred aspects of the present invention areset out in the accompanying independent and dependent claims. It will beappreciated that features of the dependent claims may be combined withfeatures of the independent claims in combinations other than thoseexplicitly set out in the claims so long as the combination istechnically possible.

Thus, the foregoing discussion discloses and describes merely exampleembodiments of the present invention. As will be understood by thoseskilled in the art, the present invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Accordingly, the disclosure of the presentinvention is intended to be illustrative, but not limiting of the scopeof the invention, as well as other claims. The disclosure, including anyreadily discernible variants of the teachings herein, defines, in part,the scope of the foregoing claim terminology such that no inventivesubject matter is dedicated to the public.

Respective features of the present disclosure are defined by thefollowing numbered paragraphs:

Clause 1. A method of determining an indication of an occupancy level ina mobile communications system, wherein the mobile communications systemcomprises a base station arranged to communicate with a mobilecommunications device via a wireless interface provided by a firstfrequency channel allocated to mobile networks communications for themobile communications system and by a shared channel which can be sharedby the mobile communications system and by other wireless communicationssystems, the method comprising a mobile communications device:

-   -   measuring, for each of a plurality of first time periods within        a second time period, a channel utilisation on the shared        channel;    -   determining channel occupancy states for the shared channel for        each of the first time periods based on the measured channel        utilisation; and    -   determining an indication of an occupancy level for the shared        channel for the second time period, wherein the indication of an        occupancy level is determined based on the occupancy states for        the shared channel for each of the first time periods.

Clause 2. A method according to any preceding clause, the method furthercomprising the mobile communications device generating a measurementreport based on the indication of an occupancy level for the sharedchannel and transmitting the measurement report to the base station.

Clause 3. A method according to Clause 2, the method comprising themobile communications device

-   -   detecting that the shared channel is congested or available when        an occupancy level for the shared channel is estimated to be        above or below, respectively, a congestion threshold; and    -   upon detecting that the shared channel is congested or        available, generating and transmitting the measurement report.

Clause 4. A method according to clause 2 or 3, the method comprising themobile communications system:

-   -   upon receipt of the measurement report, determining whether to        activate or deactivate the shared channel for uplink and/or        downlink communications with mobile communications devices based        on the indication of an occupancy level for the shared channel.

Clause 5. A method according to any of clauses 2 to 4, wherein themeasurement report is transmitted at one or more of the following times:periodically, upon receipt of a measurement request, at a randomlyselected time, upon determination of the occupancy level indication, orwhen one or more predetermined events occur.

Clause 6. A method according to any preceding clause wherein theindication of an occupancy level is determined at one or more of thefollowing times: periodically, upon receipt of a measurement request, ata randomly selected time, or when one or more predetermined eventsoccur.

Clause 7. A method according to clause 5 or 6 wherein a predeterminedevent comprises one of: a mobile communications device being powered up,a mobile communication device experiencing congestion on a frequencychannel, a user request, a mobile communications network request, theexpiry of a timer and a mobile communication device having a lowutilisation level.

Clause 8. A method according to any preceding clause wherein themeasuring step comprises the mobile communications device

-   -   determining whether the mobile communications system is        transmitting signals on the shared channel,    -   when it is determined that the mobile communications system is        transmitting signals on the shared channel, measuring the        channel utilisation based on an interference measurement        indicating an interference level identified for the signals        transmitted on the shared channel by the mobile communications        system; and    -   when it is determined that the mobile communications system is        not transmitting signals on the shared channel, measuring the        channel utilisation based on a measurement indicating a power        received via the shared channel.

Clause 9. A method according to any preceding clause wherein the mobilecommunications device comprises a first transceiver operable to receiveshared channel signals with the base station using a first technologyand a second transceiver operable to receive shared channel signalsusing a second technology, the second technology being different fromthe first technology,

-   -   wherein the method comprises the mobile communications device        measuring the channel utilisation based on a first channel        utilisation derived from signals received by the first        transceiver and on a second channel utilisation derived from        signals received by the second transceiver.

Clause 10. A mobile communications device for use in a mobilecommunications system, the system comprising a base station arranged tocommunicate with mobile communications devices via a wireless interfaceprovided by a first frequency channel allocated to mobile networkscommunications for the mobile communications system and by a sharedfrequency channel which can be shared by the mobile communicationssystem and by other wireless communications systems, the mobilecommunications device comprising:

-   -   a controller unit and    -   a transceiver unit for transmitting signals via the wireless        interface,    -   the controller unit being configured to:    -   measure, for each of a plurality of first time periods within a        second time period, a channel utilisation on the shared channel        based on signals received by the transceiver unit;    -   determine channel occupancy states for the shared channel for        each of the first time periods based on the measured channel        utilisation; and    -   determine an indication of an occupancy level for the shared        channel for the second time period, wherein the indication of an        occupancy level is determined based on the occupancy states for        the shared channel for each of the first time periods.

Clause 11. A mobile communications device according to clause 10, thecontroller unit being configured to generate a measurement report basedon the indication of an occupancy level for the shared channel and toinstruct transmission, by the transceiver unit, of the measurementreport to the base stations.

Clause 12. A mobile communications device according to clause 11, thecontroller unit being configured to

-   -   detect that the shared channel is congested when an occupancy        level for the shared channel is estimated to be above a        congestion threshold; and    -   to, upon detection that the shared channel is congested,        generate and instruct transmission of the measurement report.

Clause 13. A mobile communications device according to any of clauses 11to 12, wherein the controller unit is configured to instructtransmission of the measurement report at one or more of the followingtimes: periodically, upon receipt of a measurement request, at arandomly selected time, or when one or more predetermined events occur.

Clause 14. A mobile communications device according to any of clauses 10to 13, wherein the controller unit is configured to determine theindication of an occupancy level at one or more of the following times:periodically, upon receipt of a measurement request, at a randomlyselected time, or when one or more predetermined events occur.

Clause 15. A mobile communications device according to clause 13 or 14,wherein a predetermined event comprises one of: a mobile communicationsdevice being powered up, a mobile communication device experiencingcongestion on a frequency channel, a user request, a mobilecommunications network request, the expiry of a timer and a mobilecommunication device having a low utilisation level.

Clause 16. A mobile communications device according to any of clauses 10to 15, wherein the controller unit being configured to measure a channelutilisation on the shared channel comprises the controller unit beingconfigured

-   -   to determine whether the mobile communications system is        transmitting signals on the shared channel,    -   to measure, when it is determined that the mobile communications        system is transmitting signals on the shared channel, the        channel utilisation based on an interference measurement        indicating an interference level identified for the signals        transmitted on the shared channel on the shared channel by the        mobile communications system; and    -   to measure, when it is determined that the mobile communications        system is not transmitting signals on the shared channel, the        channel utilisation based on a measurement indicating a power        received via the shared channel.

Clause 17. A mobile communications device according to any of clauses 10to 16, the transceiver of the mobile communications device being a firsttransceiver operable to transmit and receive signals on the sharedchannel with the base station using a first technology and a secondtransceiver operable to transmit and receive signals on the sharedchannel using a second technology, the second technology being differentfrom the first technology,

-   -   wherein the controller unit is configured to measure the channel        utilisation based on a first channel utilisation derived from        signals received by the first transceiver and on a second        channel utilisation derived from signals received by the second        transceiver.

Clause 18. A mobile communications system comprising:

-   -   a base station arranged to communicate with mobile        communications devices via a wireless interface provided by a        first frequency channel allocated to mobile networks        communications for the mobile communications system and by a        shared frequency channel which can be shared by the mobile        communications system and by other wireless communications        systems; and    -   a first mobile communications device configured to:    -   measure, for each of a plurality of first time periods within a        second time period, a channel utilisation on the shared channel;    -   determine channel occupancy states for each of the first time        periods and for the shared channel based on the measured channel        utilisation; and    -   determine an indication of an occupancy level for the second        time period and for the shared channel wherein the indication of        an occupancy level is determined based on the occupancy states        for the shared channel for each of the first time periods.

Clause 19. A mobile communications system according to clause 18,wherein the first mobile communications device is configured to generatea measurement report based on the indication of an occupancy level forthe shared channel and to transmit the measurement report to the basestation.

Clause 20. A mobile communications system according to clause 19,wherein the first mobile communications device is configured to

-   -   detect that the shared channel is congested when an occupancy        level for the shared channel is estimated to be above a        congestion threshold; and    -   to, upon detecting that the shared channel is congested,        generate and transmit the measurement report.

Clause 21. A mobile communications system according to clause 19 or 20,wherein the mobile communications system is configured to

-   -   upon receipt of the measurement report, determine for at least        one of the base station whether to activate or deactivate the        shared channel for communicating with mobile communications        devices based on the indication of an occupancy level for the        shared channel.

Clause 22. A mobile communications system according to any of clauses 19to 21, wherein the first mobile communications device is configured totransmit the measurement report at one or more of the following times:periodically, upon receipt of a measurement request, at a randomlyselected time, or when one or more predetermined events occur.

Clause 23. A mobile communications system according to any of clauses 18to 22, wherein the first mobile communications device is configured todetermine the indication of an occupancy level at one or more of thefollowing times: periodically, upon receipt of a measurement request, ata randomly selected time, or when one or more predetermined eventsoccur.

Clause 24. A mobile communications system according to clause 22 or 23,wherein a predetermined event comprises one of: a mobile communicationsdevice being powered up, a mobile communication device experiencingcongestion on a frequency channel, a user request, a mobilecommunications network request, the expiry of a timer and a mobilecommunication device having a low utilisation level.

Clause 25. A mobile communications system according to any of clauses 18to 24, wherein the first mobile communications device being configuredto measure a channel utilisation comprises the first mobilecommunications device being configured to

-   -   determine whether the base station is transmitting signals on        the shared channel,    -   when it is determined that the base station is transmitting        signals on the shared channel, measure the channel utilisation        based on an interference measurement indicating an interference        level identified for the signals transmitted on the shared        channel by the mobile communications system; and    -   when it is determined that the base station is not transmitting        signals on the shared channel, measure the channel utilisation        based on a measurement indicating a power received via the        shared channel.

Clause 26. A mobile communications system according to any of clauses 18to 25, wherein the first mobile communications device comprises a firsttransceiver operable to receive signals on the shared channel from thebase station using a first technology and a second transceiver operableto receive signals on the shared channel using a second technology, thesecond technology being different from the first technology,

-   -   wherein the first mobile communications device is configured to        measure the channel utilisation based on a first channel        utilisation derived from signals received by the first        transceiver and on a second channel utilisation derived from        signals received by the second transceiver.

Clause 27. Circuitry for a mobile communications device for use in amobile communications system, the system comprising a base stationarranged to communicate with mobile communications devices via awireless interface provided by a first frequency channel allocated tomobile networks communications for the mobile communications system andby a shared frequency channel which can be shared by the mobilecommunications system and by other wireless communications systems,wherein the circuitry comprises a controller element and a transceiverelement configured to operate together to:

-   -   measure, for each of a plurality of first time periods within a        second time period, a channel utilisation on the shared channel        based on signals received by the transceiver unit;    -   determine channel occupancy states for the shared channel for        each of the first time periods based on the measured channel        utilisation; and    -   determine an indication of an occupancy level for the shared        channel for the second time period, wherein the indication of an        occupancy level is determined based on the occupancy states for        the shared channel for each of the first time periods.

REFERENCES

[1] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based radioaccess”, John Wiley and Sons, 2009[2] ETSI TS 136 211 V11.5.0 (2014 January)/3GPP TS 36.211 version 11.5.0Release 11[3] ETSI TS 136 212 V11.4.0 (2014 January)/3GPP TS 36.212 version 11.4.0Release 11[4] ETSI TS 136 213 V11.6.0 (2014 March)/3GPP TS 36.213 version 11.6.0Release 11[5] ETSI TS 136 321 V11.5.0 (2014 March)/3GPP TS 36.321 version 11.5.0Release 11[6] ETSI TS 136 331 V11.7.0 (2014 March)/3GPP TS 36.331 version 11.7.0Release 11

[7] ETSI TS 137 320 V11.3.0 (2013 April)/3GPP TS 37.320 V12.1.0 (2014June) Release 12

[8] 3GPP TR 36.805 V9.0.0 (2009 December) Release 9

[9] ETSI TS 132 422 V11.9.0 (2014 March)/3GPP TS 32.422 V12.2.0 (2014June) Release 12

What is claimed is:
 1. A mobile communications device for use in amobile communications system arranged to communicate with mobilecommunications devices via a wireless interface provided by a firstfrequency channel allocated to mobile networks communications for themobile communications system and by a shared frequency channel which canbe shared by the mobile communications system and by other wirelesscommunications systems, the mobile communications device comprising: atransceiver configured to transmit signals via the wireless interface;and circuitry configured to measure, for each of a plurality of firsttime periods within a second time period, a channel utilisation on theshared channel based on signals received by the transceiver; determinechannel occupancy states for the shared channel for each of the firsttime periods based on the measured channel utilisation; and determine anindication of an occupancy level for the shared channel for the secondtime period, wherein the indication of an occupancy level is determinedbased on the occupancy states for the shared channel for each of thefirst time periods.
 2. The mobile communications device of claim 1,wherein the circuitry is configured to generate a measurement reportbased on the indication of an occupancy level for the shared channel andto instruct transmission, by the transceiver, of the measurement reportto the mobile communications system.
 3. The mobile communications deviceof claim 2, wherein the circuitry is configured to: detect that theshared channel is congested when an occupancy level for the sharedchannel is estimated to be above a congestion threshold; and upondetection that the shared channel is congested, generate and instructtransmission of the measurement report.
 4. The mobile communicationsdevice of claim 2, wherein the circuitry is configured to instructtransmission of the measurement report at one or more of the followingtimes: periodically, upon receipt of a measurement request, at arandomly selected time, or when one or more predetermined events occur.5. The mobile communications device of claim 1, wherein the circuitry isconfigured to determine the indication of an occupancy level at one ormore of the following times: periodically, upon receipt of a measurementrequest, at a randomly selected time, or when one or more predeterminedevents occur.
 6. The mobile communications device of claim 4, wherein apredetermined event comprises one of: a mobile communications devicebeing powered up, a mobile communication device experiencing congestionon a frequency channel, a user request, a mobile communications networkrequest, the expiry of a timer and a mobile communication device havinga low utilisation level.
 7. The mobile communications device of claim 1,wherein the circuitry being configured to measure a channel utilisationon the shared channel comprises the circuitry being configured to:determine whether the mobile communications system is transmittingsignals on the shared channel, measure, when it is determined that themobile communications system is transmitting signals on the sharedchannel, the channel utilisation based on an interference measurementindicating an interference level identified for the signals transmittedon the shared channel on the shared channel by the mobile communicationssystem; and measure, when it is determined that the mobilecommunications system is not transmitting signals on the shared channel,the channel utilisation based on a measurement indicating a powerreceived via the shared channel.
 8. The mobile communications deviceaccording to claim 1, wherein the transceiver is a first transceiveroperable to transmit and receive signals on the shared channel using afirst technology and a second transceiver operable to transmit andreceive signals on the shared channel using a second technology, thesecond technology being different from the first technology, and thecircuitry is configured to measure the channel utilisation based on afirst channel utilisation derived from signals received by the firsttransceiver and on a second channel utilisation derived from signalsreceived by the second transceiver.
 9. Circuitry for a mobilecommunications device for use in a mobile communications system arrangedto communicate with mobile communications devices via a wirelessinterface provided by a first frequency channel allocated to mobilenetworks communications for the mobile communications system and by ashared frequency channel which can be shared by the mobilecommunications system and by other wireless communications systems, thecircuitry comprising: transceiver circuitry configured to transmitsignals via the wireless interface; and control circuitry configured tomeasure, for each of a plurality of first time periods within a secondtime period, a channel utilisation on the shared channel based onsignals received by the transceiver; determine channel occupancy statesfor the shared channel for each of the first time periods based on themeasured channel utilisation; and determine an indication of anoccupancy level for the shared channel for the second time period,wherein the indication of an occupancy level is determined based on theoccupancy states for the shared channel for each of the first timeperiods.
 10. The circuitry of claim 9, wherein the control circuitry isconfigured to generate a measurement report based on the indication ofan occupancy level for the shared channel and to instruct transmission,by the transceiver circuitry, of the measurement report to the mobilecommunications system.
 11. The circuitry of claim 10, wherein thecontrol circuitry is configured to: detect that the shared channel iscongested when an occupancy level for the shared channel is estimated tobe above a congestion threshold; and upon detection that the sharedchannel is congested, generate and instruct transmission of themeasurement report.
 12. The circuitry of claim 10, wherein the controlcircuitry is configured to instruct transmission of the measurementreport at one or more of the following times: periodically, upon receiptof a measurement request, at a randomly selected time, or when one ormore predetermined events occur.
 13. The circuitry of claim 9, whereinthe control circuitry is configured to determine the indication of anoccupancy level at one or more of the following times: periodically,upon receipt of a measurement request, at a randomly selected time, orwhen one or more predetermined events occur.
 14. The circuitry of claim12, wherein a predetermined event comprises one of: a mobilecommunications device being powered up, a mobile communication deviceexperiencing congestion on a frequency channel, a user request, a mobilecommunications network request, the expiry of a timer and a mobilecommunication device having a low utilisation level.
 15. The circuitryof claim 9, wherein the control circuitry being configured to measure achannel utilisation on the shared channel comprises the controlcircuitry being configured to: determine whether the mobilecommunications system is transmitting signals on the shared channel,measure, when it is determined that the mobile communications system istransmitting signals on the shared channel, the channel utilisationbased on an interference measurement indicating an interference levelidentified for the signals transmitted on the shared channel on theshared channel by the mobile communications system; and measure, when itis determined that the mobile communications system is not transmittingsignals on the shared channel, the channel utilisation based on ameasurement indicating a power received via the shared channel.
 16. Thecircuitry of claim 9, wherein the transceiver circuitry includes a firsttransceiver operable to transmit and receive signals on the sharedchannel using a first technology and a second transceiver operable totransmit and receive signals on the shared channel using a secondtechnology, the second technology being different from the firsttechnology, and the control circuitry is configured to measure thechannel utilisation based on a first channel utilisation derived fromsignals received by the first transceiver and on a second channelutilisation derived from signals received by the second transceiver. 17.A method performed by a mobile communications device for use in a mobilecommunications system arranged to communicate with mobile communicationsdevices via a wireless interface provided by a first frequency channelallocated to mobile networks communications for the mobilecommunications system and by a shared frequency channel which can beshared by the mobile communications system and by other wirelesscommunications systems, the method comprising: measuring, for each of aplurality of first time periods within a second time period, a channelutilisation on the shared channel based on signals received by themobile communications device; determining channel occupancy states forthe shared channel for each of the first time periods based on themeasured channel utilisation; and determining an indication of anoccupancy level for the shared channel for the second time period,wherein the indication of an occupancy level is determined based on theoccupancy states for the shared channel for each of the first timeperiods.